In message . com,
Graham writes
Ok Geoff,

Well that's a good milestone .. solved the inter fault by giving it a
good de-fluffing and spray with wd40 .. so far so good ..

Slippage , Its a term re pump efficiency .. simply the output leaking
back to the input .. worn impeller would have a bigger clearance so
more leakage .. less pressure .. more applicable to hp pumps ..

And what's going to wear a pump kicking water around a CH system?

Grundfos pumps (as in Vaillant 242s) have three speeds and for most
systems are set to the middle speed - if you're experiencing problems,
you could just up the speed

However, it sounds like the wind was blowing in a certain direction and
you thought "what a good day to change the pump"

if it's working, don't fiddle with it just for the sake of it

--
geoff